Feasibility of loophole-free nonlocality tests with a single photon

Recently, much interest has been directed toward designing setups that achieve realistic loss thresholds for decisive tests of local realism-in particular in the optical regime. We analyze the feasibility of such Bell tests based on a W state shared between multiple parties, which can be realized, for example, by a single photon shared between spatial modes. We develop a general error model to obtain thresholds for the efficiencies required to violate local realism and also consider two concrete optical-measurement schemes.